Purchasing of data

I have recently returned from Mozambique from my holiday and it was burning me bum to ask this question to Vodacom as well as other service providers in South Africa...Why can I get 4GB of prepaid Vodacom Data in Mozambique for R100 (400Mts) but in South Africa for 3GB I paid R330 today? Who is been ********** here? And I had friend with us in Mozambique who bought 11GB of Vodacom data for R280 (1120Mts) but here in South Africa R599? Do I feel it is fair....hmmmmm....You tell me?